Conventionally, there is provided a remote monitoring and control system that makes use of a time division multiplex signal (see, e.g., Japanese Laid-open Publication No. 11-008950, Japanese Laid-open Publication No. 5-300575, and Japanese Laid-open Publication No. 2001-086577). This kind of remote monitoring and control system is schematically shown in FIG. 28.
The remote monitoring and control system includes a transmission control unit CU, a plurality of (two, in FIG. 28) operation terminals 1 and a plurality of (two, in FIG. 28) control terminals RU. The operation terminals 1 and the control terminals RU are connected to the transmission control unit CU via a two-wire signal line Ls.
Each of the operation terminals 1 is provided with at least one control switch (four control switches in FIG. 28) having push button handle portions 51 pushed and operated by a pushing force applied from the front side thereof.
Each of the control terminals RU includes at least one relay (not shown) arranged in a power supply line leading to a load (not shown) such as an illumination device or a ventilating fan. The load is on-off controlled by on-off controlling the relay.
Individual addresses are allotted to the respective control switches and the respective loads (more exactly, the respective relays). The number of addresses available in the system as a whole is two hundred fifty six (256) in total, which is the product of sixty four (64) channels numbered from 0 to 63 and four (4) circuits numbered from 1 to 4. Each of the addresses is identified as, e.g., 63-3, using the channel number and the circuit number.
The transmission control unit CU delivers, through the signal line Ls, a transmission signal Vs with a format illustrated in FIG. 29A. In other words, the transmission signal Vs is a time division multiplex signal, which is a bipolar signal (±24 V), including a synchronization signal SP indicative of signal delivery commencement, mode data MD indicative of the mode of the transmission signal Vs, address data AD for use in specifically calling out the operation terminals 1 or the control terminals RU, control data CD for use in controlling the load, checksum data CS for use in detecting a transmission error and a response waiting time slot WT, i.e., a time slot during which to receive a response signal (i.e., monitoring data) from the operation terminals 1 or the control terminals RU. With the transmission signal Vs, data are transmitted through pulse width modulation as illustrated in FIG. 29B.
If the address data AD of the transmission signal Vs received through the signal lines Ls coincide with a pre-set address, the operation terminals 1 and the control terminals RU capture the control data CD from the transmission signal Vs and return monitoring data, as a current mode signal (a signal delivered by short-circuiting the signal lines Ls via suitable low impedance), to the transmission control device 100 during the response waiting time slot WT.
In case where data are delivered from the transmission control unit CU to a desired one of the operation terminals 1 and the control terminals RU, the transmission control unit CU delivers a transmission signal Vs whose mode data MD is in a control mode and whose address data AD is matched with the address of one of the operation terminals 1 or the control terminals RU. As the transmission signal Vs is delivered to the signal line Ls, the operation terminals 1 or the control terminals RU, whichever have an address coinciding with the address data AD, capture the control data CD and return monitoring (status) data to the transmission control unit CU during the response waiting time slot WT. Based on the relationship between the control data CD delivered and the monitoring data received during the response waiting time slot WT, the transmission control unit CU conforms that the control data CD have been transmitted to the desired operation terminal 1 or the desired control terminal RU. The control terminal RU outputs a control signal for controlling a load according to the control data CD received. The operation terminal 1 outputs an indication signal for identifying and indicating the operation of the load according to the control data CD received.
At normal times, the transmission control unit CU is periodically delivering the transmission signal Vs in which the mode data MD is in a dummy mode (this will be referred to as “normal polling”). In this case, the transmission control unit CU gains access to an arbitrary one of the control terminals RU and requests it to send the monitoring data indicative of a load status back to the transmission control unit CU. Responsive this request, the control terminal RU sends back to the transmission control unit CU the monitoring data indicative of the status of a load connected thereto. Upon receiving the reply, the transmission control unit CU gains access to the address of the operation terminal 1 corresponding to the control terminal RU and transmit to the operation terminal 1 the control data CD needed to indicate the status of the load connected to the control terminal RU.
In this manner, the operation of gaining access to the addresses of the control terminal RU and the operation terminal 1 corresponding thereto is cyclically repeated in the normal polling.
When an attempt is made to transmit certain information to the transmission control unit CU during the normal polling times, an interrupt signal Vi as shown in FIG. 29C is generated in synchronization with the synchronization signal SP of the dummy-mode transmission signal Vs. At this time, the operation terminal 1 sets an interrupt flag in preparation for the subsequent information delivery to and from the transmission control unit CU. Upon receiving the interrupt signal Vi, the transmission control unit CU delivers a transmission signal while setting the mode data MD in an interrupt polling mode and gradually increasing the upper half bits of the address data AD (the upper four bits in case of the address data AD being eight bits).
If the upper four bits of the address data AD of the transmission signal delivered in the interrupt polling mode coincide with the upper four bits of the address of the operation terminal 1, the operation terminal 1 that has generated the interrupt signal Vi sends the lower four bits of the address thereof back to the transmission control unit CU during the response waiting time slot WT. In this manner, the transmission control unit CU searches for sixteen operation terminals 1 at one time to find the one that has generated the interrupt signal Vi. This makes it possible to find the operation terminal 1 within a relatively short period of time.
Once the transmission control unit CU acquires the address of the operation terminal 1 that has generated the interrupt signal Vi, it delivers to the signal line Ls a transmission signal Vs which contains the mode data in a monitoring mode and the address data AD indicative of the address thus acquired. Responsive to this transmission signal Vs, the operation terminal 1 sends back to the transmission unit 105a the information sought for transmission within the response waiting time slot WT. Finally, the transmission control unit CU delivers a signal by which the operation terminal 1 that has generated the interrupt signal Vi is instructed to reset the interrupt, thereby canceling the interrupt flag.
In the manner as set forth above, the information transmission from the operation terminal 1 to the transmission control unit CU is completed by transmitting signals (including the dummy mode signal, the interrupt polling mode signal, the monitoring mode signal and the interrupt reset signal) four times from the transmission control unit CU to the operation terminal 1. In order for the transmission control unit CU to learn the operating status of a desired one of the control terminals RU, it is sufficient to merely deliver a transmission signal in which the mode data MD is in the monitoring mode.
If the push button handle portion 51 of one of the control switches is pushed, the operation terminal 1 sends back to the transmission control unit CU the monitoring data which contains information on the address of the control switch whose push button handle portion 51 is pushed. The transmission control unit CU generates control data CD using this monitoring data and transmits a transmission signal Vs containing the control data CD to the control terminal RU. The control terminal RU controls a load according to the control data CD contained in the transmission signal Vs. After controlling the load, the control terminal RU sends monitoring data back to the transmission control unit CU. Responsive to this monitoring data, the transmission control unit CU generates a transmission signal Vs containing the control data CD needed to indicate the operating status of the load and transmits the transmission signal Vs to the operation terminal 1. In response to this transmission signal Vs, the operation terminal 1 turns on or off a light-emitting unit that indicates the operating status of the load. The light-emitting unit includes a light-emitting element (not shown) such as a light-emitting diode or the like and a light guide portion 41 made of a transparent material and exposed to the front surface of the operation terminal 1 as shown in FIGS. 30 through 32. The light generated from the light-emitting element is projected frontwards through the light guide portion 41.
Some of the operation terminals 1 have a single light-emitting unit (a single light guide portion 41) for one control switch (one push button handle portion 51) as illustrated in FIG. 30. Others have two light-emitting units (two light guide portions 41) for one control switch (one push button handle portion 51) as illustrated in FIGS. 31 and 32.
The two light-emitting units are differently operated to emit light. For example, one of the two light-emitting units (e.g., the upper one in FIG. 31 or the right one in FIG. 32) emits light when the load is in an on-state, while the other (e.g., the lower one in FIG. 31 or the left one in FIG. 32) emits light when the load is in an off-state.
On the front surface of the operation terminal 1 shown in FIG. 31 or 32, there is provided a signal input window 62b through which an optical signal is inputted from an address setting device (not shown) for setting addresses of the control switches.
In case where two light-emitting units are provided as shown in FIGS. 31 and 32, it is typical that the light-emitting units are operated in different colors. For example, the light-emitting unit energized in the on-state of the load is designed to emit red light, while the light-emitting unit energized in the off-state of the load is designed to emit green light. However, it is sometimes the case that one who suffers from color blindness has a difficulty in discerning the light colors. In particular, if the two light-emitting units (two light guide portions 41) corresponding to the same control switch (the same push button handle portion 51) are arranged adjacent to each other as shown in FIG. 31, it is much more difficult for the color-blind person to discern the operating status of the load.
This problem is ameliorated if the two light-emitting units (the two light guide portions 41) corresponding to the same control switch (the same push button handle portion 51) are spaced apart from each other as shown in FIG. 32. Since the four control switches and the light-emitting units corresponding thereto are all arranged one above another along the vertical direction in the example shown in FIG. 32, it is difficult to figure out the correspondence relationship between the control switches and the light-emitting units. In other words, it is difficult to determine at a glance whether each of the light-emitting units interposed between the control switches (the push button handle portions 51), e.g., the second light-emitting unit (the second light guide portion 41) counted from the top in FIG. 32, corresponds to the upper control switch or the lower control switch.
In case that a plurality of light guide portions 41 are used for the operation terminal 1 as shown in FIGS. 31 and 32, if each light guide portion 41 is configured as separate part, manufacturing cost is raised due to increased number of parts.
The above mentioned address setting device is capable of setting four addresses of the control switch at once. Accordingly, if the addresses of operation terminal 1 having eight control switches are made to be set by optical signals from the address setting device above, there is required two light-receiving unit in each control switch 4 because each four control switches 4 is required one light-receiving unit. In this case, if an optical signal targeting one light-receiving unit is received by the other light-receiving unit, an address is set to unintended control switch.